The present invention is directed to lamp structure having elliptical reflectors, and methods of use thereof, for more uniformly irradiating surfaces of at least one workpiece (for example, a continuous workpiece such as a continuous fiber and/or filament). The present invention is particularly directed to apparatus, and methods, for more uniformly irradiating optical fibers, cables and ribbons, which continuously pass by a bulb, of the lamp, generating the radiation, within an elliptical space formed by the reflectors.
The present invention is especially useful in connection with irradiating a workpiece passing along a lamp bulb producing, for example, infrared light, visible light or ultraviolet light, in the processing of workpieces to cure a photo-responsive coating (for example, ultraviolet light curable coatings, and coloring inks) on surfaces of the workpieces.
The present invention has uses within the optical fiber market, including methods for processing fibers, ribbons and cables of various widths and thickness cross-sections, multi-fiber coloring, strengthening members and other applications that require a pattern of radiant flux density to the workpieces being processed.
Conventional apparatus (systems) for irradiating a fiber or ribbon with ultraviolet light includes a lamp (for example, a modular lamp, such as a microwave-powered lamp having a microwave-powered bulb (e.g., tubular bulb) with no electrodes or glass-to-metal seals), the lamp having reflectors. The reflectors can desirably utilize a primary elliptical-shaped reflector and also a secondary elliptical-shaped reflector (which optionally can have a cylindrical back reflector). This reflector structure of primary and secondary elliptical-shaped reflectors is illustrated in FIG. 1, which shows the structure of xe2x80x9cDRF Systemsxe2x80x9d (ultraviolet curing systems for optical fiber, coloring, ribbon and cable) of Fusion UV Systems, Inc.
Thus, shown in FIG. 1 is bulb 1 (e.g., a tubular bulb), centered at first focal point 2. Hereinafter, when it is stated herein that the bulb is positioned at a location, it is meant that the bulb is centered at such location. This first focal point 2 is one of the two focal points in elliptical space 4 surrounded by primary elliptical-shaped reflector 3 and secondary elliptical-shaped reflector 9. The second focal point of this elliptical space 4 is designated by reference character 6, at which point optical fiber 5 is centered. Also shown in FIG. 1 is quartz tube 7, through which optical fiber 5 passes. Quartz tube 7 is preferred in order to be able to provide a desired atmosphere (for example, an inert gas atmosphere) surrounding optical fiber 5, without the need for filling the entire elliptical space 4 with such inert gas. Also shown in FIG. 1 is cylindrical back (auxiliary) reflector 11.
As seen in FIG. 1, light 12 from bulb 1, either directly or more likely after being reflected by reflectors 3, 9 and/or 11, is transmitted through quartz tube 7 to be irradiated on, e.g., optical fiber 5 to perform a process thereon (for example, cure a coating on the optical fiber).
In the structure shown in FIG. 1, bulb 1 is positioned at first focal point 2 of elliptical space 4 formed by primary elliptical-shaped reflector 3 and secondary elliptical-shaped reflector 9, and the workpiece runs through second focal point 6 of elliptical space 4.
FIG. 2 shows a standard ray diagram for conventional xe2x80x9cDRF Systemsxe2x80x9d of Fusion UV Systems, Inc., having primary and secondary elliptical-shaped reflectors 3 and 9, but without a cylindrical back reflector 11. Bulb 1 is positioned at first focal point 2 of the elliptical space 4 of the reflector, that is, a position 1.900 inches from a midpoint of the major axis of the elliptical space 4.
That is, FIG. 2 shows the standard I25X/I60X ray diagram for the apparatus having primary and second elliptical-shaped reflectors 3 and 9, respectively with a distance of 4.271 inches between bulb 1 and fiber 5 and an entire distance between the ends of the primary and secondary elliptical-shaped reflectors being 6.000 inches. A maximum width of the reflectors is 4.214 inches. As shown in this standard ray diagram of FIG. 2, bulb 1 and fiber 5 are respectively at the primary and secondary focal points 2, 6 of elliptical space 4; light 12 from bulb 1 is substantially transmitted to fiber 5 passing through second focal point 2 of the elliptical space 4.
However, various problems arise in connection with use of this conventional structure. For one thing, alignment of the fiber 5 at secondary focal point 6 is critical, but can be difficult to achieve.
In addition, focusing of light rays 12 at second focal point 6 can cause problems in uniformity when, for example, the fiber or fibers being treated are not solely at second focal point 6. For example, where a ribbon is being processed which has a planar surface having a width perpendicular to the direction of motion of the ribbon (that is, in a width direction of elliptical space 4 shown in FIG. 1), focusing of light rays 12 at second focal point 6 causes non-uniformity of light irradiating on the ribbon. Such non-uniformity is especially disadvantageously great for light irradiating the surface of the ribbon facing bulb a compared with light irradiating the surface of the ribbon facing away from bulb 1.
In order to avoid the aforementioned problems of conventional structure, a proposed technique would be to position the workpiece slightly away from the second focal point 6, so that a pattern of radiation spaced from second focal point 6 impinges on the workpiece. This is shown in FIG. 3, where ribbon 15 is displaced slightly from second focal point 6, in a direction along major axis 22 of elliptical space 4, toward secondary elliptical-shaped reflector 9. However, this technique of moving the workpiece does not in and of itself provide sufficient uniformity of radiation pattern on surfaces of ribbon 15.
Accordingly, it is desired to provide apparatus and methods of use of such apparatus, providing a more uniform irradiation of all surfaces of the workpiece, including workpiece surfaces facing the bulb and surfaces facing away from the bulb, using elliptical-shaped reflector structure. It is desired to provide such more uniform irradiation of surfaces of the workpiece, without the need for providing precise positioning of the workpiece at the second focal point, and wherein the apparatus can be utilized to process, e.g., fibers, ribbons and cables of various widths and thickness cross-sections.
The present invention overcomes deficiencies of the above-described techniques, achieving a more uniform dispersion of light over the surfaces of the workpieces, by moving the bulb such that the bulb is spaced from the first focal point. That is, while, according to conventional techniques, the center of the bulb is at the first focal point, according to the present invention the center of the bulb is spaced from the first focal point of the ellipse. According to the present invention, the bulb is positioned spaced from the first focal point of the ellipse in the vicinity thereof, on the major axis of the ellipse.
Thus, according to one aspect of the present invention, structure of a lamp for irradiating at least one workpiece, this structure including reflector structure, is provided. The reflector includes primary and secondary elliptical-shaped reflectors, these two reflectors in combination forming substantially an ellipse, surrounding an elliptical space, with the ellipse having a major axis and first and second focal points, the first focal point being closer to the primary reflector than the second focal point is to this primary reflector, along the major axis. This structure of the lamp includes support structure for a bulb of this lamp, to support the bulb within the elliptical space, so that the bulb is spaced from the first focal point of the ellipse in the vicinity thereof, on the major axis of the ellipse.
As a further aspect of this invention, a lamp is provided including the bulb, spaced from this first focal point of the ellipse.
According to the present invention, the bulb can be displaced from the first focal point, along the major axis, either in a direction toward the primary elliptical-shaped reflector or in a direction away from the primary elliptical-shaped reflector (that is, in a direction toward the secondary elliptical-shaped reflector). The bulb is to be maintained in the vicinity of the first focal point, in order to achieve objectives according to the present invention.
As another aspect of the present invention, the structure, including the reflector structure, also includes end reflectors covering both ends of the primary elliptical-shaped reflector, but, for example, not extending beyond the ends of this primary reflector. The end reflectors can be provided with a support (for example, holes) for supporting the bulb of the lamp.
According to further aspects of the present invention, each of the primary and secondary elliptical-shaped reflectors extends in a longitudinal direction and is positioned so as to form, in combination, a cylinder having an axis extending in the longitudinal direction. The bulb can be a tubular bulb having an axis extending in this longitudinal direction, and the workpiece or workpieces can be passed in this longitudinal direction along the bulb, during processing.
According to other aspects of the present invention, the workpieces treated are processed while in the vicinity of the second focal point, on the aforementioned major axis. That is, the workpiece or workpieces being treated can be at the second focal point (that is, centered at the second focal point) or displaced therefrom, along the major axis, either in a direction toward the primary elliptical-shaped reflector or secondary elliptical-shaped reflector while still in a vicinity of the second focal point.
In the foregoing, it has been described that the bulb and the at least one workpiece being processed respectively are in the vicinity of the first focal point of the ellipse, along the major axis thereof, but not at the first focal point; and in the vicinity of the second focal point of the ellipse, along the major axis thereof. By xe2x80x9cin the vicinity of the first focal point, but not at the first focal pointxe2x80x9d, means that the bulb is closer to the first focal point than to the second focal point, but is not at the first focal point so as to achieve dispersion of rays arriving in the vicinity of the second focal point, providing more uniformity according to the present invention. The positioning of the workpieces in the vicinity of the second focal point means that the workpieces can be centered on a major axis closer to the second focal point than to the first focal point, and sufficiently distanced from the bulb to achieve substantial uniformity. The workpieces can be centered at the second focal point; thus, workpieces in the vicinity of the second focal point includes the workpieces being centered at the second focal point.
According to the present invention, the light provided by the bulb can be any of various types, including at least one of ultraviolet light, infrared light and visible light. Various different types of bulbs can be utilized. For example, a bulb of an arc lamp can be utilized, for providing ultraviolet light. As an alternative, the bulb can be a microwave-powered, ultraviolet light-generating electrodeless bulb; that is, microwaves can be applied to such bulb to generate ultraviolet light which is reflected by the elliptical-shaped reflectors and irradiates the workpieces.
The present invention, as another aspect thereof, also includes apparatus for irradiating surfaces of the periphery of at least one workpiece, including the aforementioned elliptical-shaped reflectors and the bulb positioned on the major axis of the elliptical space formed by the reflectors, spaced from the first focal point of this elliptical space and in the vicinity of this first focal point. This apparatus includes structure for passing the at least one workpiece through the space surrounded by the primary and secondary elliptical-shaped reflectors, passing the at least one workpiece, e.g., in the vicinity of the second focal point of the elliptical space at a location centered on the major axis. According to additional aspects of the present invention, the at least one workpiece treated can be a continuous member, such as a continuous fiber, ribbon or cable. According to a specific apparatus, the workpieces processed can be optical fibers.
Additional aspects of the present invention include methods of using this apparatus, for substantially uniformly irradiating surfaces of at least one workpiece passing through the elliptical space in the vicinity of the second focal point, utilizing energy radiated from a bulb which is positioned on the major axis of the elliptical space formed by primary and secondary elliptical-shaped reflectors, in the vicinity of the first focal point of this elliptical space yet spaced from this first focal point. According to this process, as the at least one workpiece is passed through the space surrounded by the primary and secondary reflectors, in the vicinity of the second focal point, light is radiated from the bulb, the light reflecting off the reflectors to irradiate surfaces of the periphery of the at least one workpiece.
According to a specific use of this apparatus, as an aspect of the present invention, the apparatus can be used to cure an ultraviolet light curable coating on at least one workpiece. That is, the at least one workpiece, having the ultraviolet curable coating thereon, is passed through the space surrounded by the primary and secondary elliptical-shaped reflectors, in the vicinity of the second focal point of this elliptical space; and while performing such passing, ultraviolet light radiated from a bulb positioned on the major axis in the vicinity of the first focal point of this elliptical space, yet spaced from this first focal point, and reflecting off the primary and secondary reflectors, irradiates surfaces of the periphery of the at least one workpiece to cure the ultraviolet light curable coating.
Accordingly, by the various aspects of the present invention, uniformity of irradiation (for example, uniformity of intensity of the radiation) on all surfaces of the workpieces (both surfaces facing the bulb and surfaces facing away from the bulb) is improved, even for treatment of ribbons having, for example, substantially planar surfaces that are wide. In addition, a need for precision in placement of the workpieces, at the focal point, can be avoided.